System and method for resetting an implantable medical device

ABSTRACT

In one embodiment, a method, of operating an implantable medical device, comprises: (i) operating reset logic within the implantable medical device that is independently operable from a processor of the implantable medical device after the implantable medical device is implanted within a patient, wherein the processor is adapted for central control of the implantable medical device; (ii) operating a magnetic field sensor in the implantable medical device; (iii) generating digital data using, at least, the magnetic field sensor; (iv) detecting, by the reset logic, a digital key in the digital data; (v) in response to (iv), asserting a reset signal on a pin of the processor by the reset logic; and (vi) conducting reset operations in the processor in response to the reset signal.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/593,233, filed Aug. 23, 2012 which claims the benefit ofU.S. Provisional Patent Application Ser. No. 61/548,614, filed Oct. 18,2011, which are incorporated herein by reference.

BACKGROUND

The medical device industry produces a wide variety of electronic andmechanical devices for addressing patient medical conditions. Cliniciansuse medical devices alone or in combination with drug therapies andsurgery to address numerous patient medical conditions. Medical devicesmay provide the best and sometimes the only therapy for selected medicalconditions and disorders. Common implantable medical devices includeneurostirnulation systems, pacemakers, defibrillators, drug deliverypumps, and diagnostic recorders.

For example, neurostimulation systems are devices that generateelectrical pulses and deliver the pulses to nerve tissue to treat avariety of disorders. Spinal cord stimulation (SCS) is the most commontype of neurostimulation. In SCS, electrical pulses are delivered tonerve tissue in the spine typically for the purpose of chronic paincontrol, While a precise understanding of the interaction between theapplied electrical energy and the nervous tissue is not fullyappreciated, it is known that application of an electrical field tospinal nervous tissue can effectively mask certain types of paintransmitted from regions of the body associated with the stimulatednerve tissue. Specifically, applying electrical energy to the spinalcord associated with regions of the body afflicted with chronic pain caninduce “paresthesia” (a subjective sensation of numbness or tingling) inthe afflicted bodily regions. Thereby, paresthesia can effectively maskthe transmission of non-acute pain sensations to the brain.

SCS systems generally include a pulse generator and one or more leads, Astimulation lead includes a lead body of insulative material thatencloses wire conductors. The distal end of the stimulation leadincludes multiple electrodes that are electrically coupled to the wireconductors. The proximal end of the lead body includes multipleterminals, which are also electrically coupled to the wire conductors,that are adapted to receive electrical pulses. The distal end of arespective stimulation lead is implanted within the epidural space todeliver the electrical pulses to the appropriate nerve tissue within thespinal cord that corresponds to the dermatome(s) in which the patientexperiences chronic pain. The stimulation leads are then tunneled toanother location within the patient's body to be electrically connectedwith a pulse generator or, alternatively, to an “extension.”

The pulse generator is typically implanted within a subcutaneous pocketcreated during the implantation procedure. In SCS, the subcutaneouspocket is typically disposed in a lower back region, althoughsubclavicular implantations and lower abdominal implantations arecommonly employed for other types of neuromodulation therapies,

The pulse generator is typically implemented using a metallic housingthat encloses circuitry for generating the electrical pulses, controlcircuitry, communication circuitry, a rechargeable battery, etc. Thepulse generating circuitry is coupled to one or more stimulation leadsthrough electrical connections provided in a “header” of the pulsegenerator. Specifically, feedthrough wires typically exit the metallichousing and enter into a header structure of a moldable material. Withinthe header structure, the feedthrough wires are electrically coupled toannular electrical connectors. The header structure holds the annularconnectors in a fixed arrangement that corresponds to the arrangement ofterminals on a stimulation lead.

SUMMARY

In one embodiment, a method, of operating an implantable medical device,comprises: (i) operating reset logic within the implantable medicaldevice that is independently operable from a processor of theimplantable medical device after the implantable medical device isimplanted within a patient, wherein the processor is adapted for centralcontrol of the implantable medical device; (ii) operating a magneticfield sensor in the implantable medical device; (iii) generating digitaldata using, at least, the magnetic field sensor; (iv) detecting, by thereset logic, a digital key in the digital data; (v) in response to (iv),asserting a reset signal on a pin of the processor by the reset logic;and (vi) conducting reset operations in the processor in response to thereset signal.

The foregoing has outlined rather broadly certain features and/ortechnical advantages in order that the detailed description that followsmay be better understood. Additional features and/or advantages will bedescribed hereinafter which form the subject of the claims. It should beappreciated by those skilled in the art that the conception and specificembodiment disclosed may be readily utilized as a basis for modifying ordesigning other structures for carrying out the same purposes. It shouldalso be realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the appendedclaims. The novel features, both as to organization and method ofoperation, together with further objects and advantages will be betterunderstood from the following description when considered in connectionwith the accompanying figures, it is to be expressly understood,however, that each of the figures is provided for the purpose ofillustration and description only and is not intended as a definition ofthe limits of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a stimulation system according to some representativeembodiments.

FIG. 2A depicts one electrode configuration at the distal end of a leadthat may be employed in stimulator systems according to somerepresentative embodiments,

FIG. 2B depicts another electrode configuration at the distal end of alead that may be employed in stimulator systems according to somerepresentative embodiments.

FIG. 2C depicts another electrode configuration at the distal end of alead that may be employed in stimulator systems according to somerepresentative embodiments.

FIG. 3 depicts circuitry involved in a reset operation of an implantedmedical device according to some representative embodiments.

FIG. 4 depicts a flowchart of operations involved in resetting animplanted medical device according to some representative embodiments.

DETAILED DESCRIPTION

FIG. 1 depicts stimulation system 100 that generates electrical pulsesfor application to tissue of a patient according to some representativeembodiments. For example, system 100 may be adapted to stimulate spinalcord tissue, peripheral nerve tissue, deep brain tissue, corticaltissue, cardiac tissue, digestive tissue, pelvic floor tissue, or anyother suitable tissue within a patient's body. Although a stimulationsystem is described according to some embodiments, any implantablemedical device may be reset according to other embodiments.

The stimulation system includes implantable pulse generator 150 that isadapted to generate electrical pulses for application to tissue of apatient, implantable pulse generator 150 typically comprises a metallichousing that encloses controller 151, pulse generating circuitry 152,charging component 153, battery 154, far-field and/or near fieldcommunication circuitry 155, battery charging circuitry 156, switchingcircuitry 157, etc, of the device, Controller 151 typically includes amicrocontroller or other suitable processor for controlling the variousother components of the device. Software code is typically stored inmemory of the pulse generator 150 for execution by the microcontrolleror processor to control the various components of the device.

Although not required, in this specific embodiment, pulse generator 150comprises attached extension component 170. That is, in lieu ofproviding a separate extension lead that is physically placed within aheader of an IPG by the surgeon during Implant, extension component 170is directly attached to and is non-removable from pulse generator 150according to some representative embodiments. Other embodiments mayemploy a separate extension component 170 for connecting stimulationlead 110 with the generator 150. Alternatively, stimulation lead 110 maybe directly coupled within the header of the generator 150. Within pulsegenerator 150, electrical pulses are generated by pulse generatingcircuitry 152 and are provided to switching circuitry 157. The switchingcircuit connects to output wires, traces, lines, or the like (not shownin FIG. 1) which are, in turn, electrically coupled to internalconductive wires (not shown in FIG. 1) of lead body 172 of extensioncomponent 170. The conductive wires, in turn, are electrically coupledto electrical connectors (e.g., “Bal-Seal” connectors) within connectorportion 171 of extension component 170.

The terminals of one or more stimulation leads 110 are inserted withinport 175 of connector portion 171 for electrical connection withrespective electrical connectors (not shown) within connector portion171. Connector portion 171 may include one or more set-screw mechanisms(not shown) to secure the lead(s) 110 within connector portion 171. Thepulses originating from pulse generator 150 and conducted through theconductors of lead body 172 are provided to stimulation lead 110. Thepulses are then conducted through the conductors of lead 110 and appliedto tissue of a patient via electrodes 111. Any suitable known or laterdeveloped design may be employed for connector portion 171. Also,connector portion 171 may include multiple ports 175 for receipt of asuitable number of stimulation leads 110.

Although not required, extension component 170 is arranged to place port175 in a specific arrangement relative to the housing of pulse generator150 (as shown in FIG. 1). Specifically, when lead body 172 is disposedin a linear configuration and extends away substantially perpendicularlyfrom the housing of pulse generator 150, port 175 preferably faces thehousing of pulse generator 150. That is, at least one port 175 is on theside of extension component 170 that is proximal to housing of pulsegenerator 150, i.e. the side on which lead body 172 meets connectorportion 171. Also, when the terminals of lead 110 are placed withinconnector portion 171, lead 110 initially extends back toward thehousing of pulse generator 150. In other embodiments, any suitable formfactor may be employed for generator 150 according to other embodiments.Also, extension component 170 may be implemented as a separate discretecomponent from generator 150 as is known in the art.

Also, at any suitable time, the clinician may input data into controllerdevice 160 (see below) indicating the ports 175 in which leads 110 areplaced, thereby permitting controller device 160 to properly correlatethe various electrodes and terminals of lead 110 to the correspondingelectrical connectors of connector portion 171.

For implementation of the components within puke generator 150, aprocessor and associated charge control circuitry for an implantablepulse generator is described in U.S. Patent Publication No. 20060259098,entitled “SYSTEMS AND METHODS FOR USE IN PULSE GENERATION,” which isincorporated herein by reference. Circuitry for recharging arechargeable battery of an implantable pulse generator using inductivecoupling and external charging circuits are described in U.S. patentSer. No. 11/109,114, entitled “IMPLANTABLE DEVICE AND SYSTEM FORWIRELESS COMMUNICATION,” which is incorporated herein by reference.

An example and discussion of “constant current” pulse generatingcircuitry is provided in U.S. Patent Publication No. 20060170486entitled “PULSE GENERATOR HAVING AN EFFICIENT FRACTIONAL VOLTAGECONVERTER AND METHOD OF USE,” which is incorporated herein by reference.One or multiple sets of such circuitry may be provided within pulsegenerator 150. Different pulses on different electrodes may be generatedusing a single set of pulse generating circuitry using consecutivelygenerated pulses according to a “multi-stimset program” as is known inthe art. Alternatively, multiple sets of such circuitry may be employedto provide pulse patterns that include simultaneously generated anddelivered stimulation pulses through various electrodes of one or morestimulation leads as is also known in the art. Various sets ofparameters may define the pulse characteristics and pulse timing for thepulses applied to various electrodes as is known in the art. Althoughconstant current pulse generating circuitry is contemplated for someembodiments, any other suitable type of pulse generating circuitry maybe employed such as constant voltage pulse generating circuitry.

Stimulation lead(s) 110 may comprise a lead body of insulative materialabout a plurality of conductors within the material that extend from aproximal end of lead 110 to its distal end. The conductors electricallycouple a plurality of electrodes 111 to a plurality of terminals (notshown) of lead 110. The terminals are adapted to receive electricalpulses and the electrodes 111 are adapted to apply stimulation pulses totissue of the patient, Also, sensing of physiological signals may occurthrough electrodes 111, the conductors, and the terminals. Additionallyor alternatively, various sensors (not shown) may be located near thedistal end of stimulation lead 110 and electrically coupled to terminalsthrough conductors within the lead body 172. Stimulation lead 110 mayinclude any suitable number of electrodes 111, terminals, and internalconductors. Likewise, connector portion 171 may comprise any suitablenumber of electrical connectors and lead body 172 may comprise anysuitable number of conductors.

FIGS. 2A-2C respectively depict stimulation portions 200, 225, and 250for inclusion at the distal end of lead 110. Stimulation portion 200depicts a conventional stimulation portion of a “percutaneous” lead withmultiple ring electrodes. Stimulation portion 225 depicts a stimulationportion including several “segmented electrodes.” The term “segmentedelectrode is distinguishable from the term ring electrode.” As usedherein, the term “segmented electrode” refers to an electrode of a groupof electrodes that are positioned at the same longitudinal locationalong the longitudinal axis of a lead and that are angularly positionedabout the longitudinal axis so they do not overlap and are electricallyisolated from one another. Example fabrication processes are disclosedin U.S. Provisional Patent Application Ser. No. 61/247,360, entitled,“METHOD OF FABRICATING STIMULATION LEAD FOR APPLYING ELECTRICALSTIMULATION TO TISSUE OF A PATIENT,” which is incorporated herein byreference, Stimulation portion 250 includes multiple planar electrodeson a paddle structure. Any suitable stimulation portion design may beemployed for lead 110.

Although not required for all embodiments, the lead bodies of lead(s)110 and extension component 170 may be fabricated to flex and elongatein response to patient movements upon implantation within the patient.By fabricating lead bodies according to some embodiments manner, a leadbody or a portion thereof is capable of elastic elongation underrelatively low stretching forces. Also, after removal of the stretchingforce, the lead body is capable of resuming its original length andprofile. For example, the lead body may stretch 10%, 20%, 25%, 35%, oreven up or above to 50% at forces of about 0.5, 1.0, and/or 2.0 poundsof stretching force.

The ability to elongate at relatively low forces may present one or moreadvantages for implantation in a patient, For example, as a patientchanges posture (e.g., “bends” the patient's back), the distance fromthe implanted pulse generator to the stimulation target locationchanges. The lead body may elongate in response to such changes inposture without damaging the conductors of the lead body ordisconnecting from pulse generator. Also, deep brain stimulationimplants, cortical stimulation implants, and occipital subcutaneousstimulation implants usually involve tunneling of the lead body throughtissue of the patient's neck to a location below the clavicle. Movementof the patient's neck subjects a stimulation lead to significant flexingand twisting which may damage the conductors of the lead body. Due tothe ability to elastically elongate responsive to movement of thepatient's neck, certain lead bodies according to some embodiments arebetter adapted for such implants than some other known lead bodydesigns. Fabrication techniques and material characteristics for “bodycompliant” leads are disclosed in greater detail in U.S. ProvisionalPatent Application Ser. No. 60/788,518, entitled “Lead BodyManufacturing,” filed Mar. 31, 2006, which is incorporated herein byreference.

Controller device 160 may be implemented to recharge battery 154 ofpulse generator 150 (although a separate recharging device couldalternatively be employed). A “wand” 165 may be electrically connectedto controller device through suitable electrical connectors (not shown).The electrical connectors are electrically connected to coil 166 (the“primary” coil) at the distal end of wand 165 through respective wires(not shown). Typically, coil 166 is connected to the wires throughcapacitors (not shown). Also, in some embodiments, wand 165 may compriseone or more temperature sensors for use during charging operations.

The patient then places the primary coil 166 against the patients bodyimmediately above the secondary coil (not shown), i.e., the coil of theimplantable medical device. Preferably, the primary coil 166 and thesecondary coil are aligned in a coaxial manner by the patient forefficiency of the coupling between the primary and secondary coils.Controller 160 generates an AC signal to drive current through coil 166of wand 165. Assuming that primary coil 166 and secondary coil aresuitably positioned relative to each other, the secondary coil isdisposed within the field generated by the current driven throughprimary coil 166. Current is then induced in secondary coil, The currentinduced in the coil of the implantable pulse generator is rectified andregulated to recharge battery 154 by charging circuitry 156. Chargingcircuitry 156 may also communicate status messages to controller 160during charging operations using pulse-loading or any other suitabletechnique. For example, controller 160 may communicate the couplingstatus, charging status, charge completion status, etc.

External controller device 160 is also a device that permits theoperations of pulse generator 150 to be controlled by user after pulsegenerator 150 is implanted within a patient, although in alternativeembodiments separate devices are employed for charging and programming.Also, multiple controller devices may be provided for different types ofusers (e.g., the patient or a clinician). Controller device 160 can beimplemented by utilizing a suitable handheld processor-based system thatpossesses wireless communication capabilities, Software is typicallystored in memory of controller device 160 to control the variousoperations of controller device 160. Also, the wireless communicationfunctionality of controller device 160 can be integrated within thehandheld device package or provided as a separate attachable device. Theinterface functionality of controller device 160 is implemented usingsuitable software code for interacting with the user and using thewireless communication capabilities to conduct communications with IPG150.

Controller device 160 preferably provides one or more user interfaces toallow the user to operate pulse generator 150 according to one or morestimulation programs to treat the patient's disorder(s). Eachstimulation program may include one or more sets of stimulationparameters including pulse amplitude, pulse width, pulse frequency orinter-pulse period, pulse repetition parameter (e.g., number of timesfor a given pulse to be repeated for respective stimset during executionof program), etc. IPG 150 modifies its internal parameters in responseto the control signals from controller device 160 to vary thestimulation characteristics of stimulation pulses transmitted throughstimulation lead 110 to the tissue of the patient. Neurostimulationsystems, stir sets, and multi-stirnset programs are discussed in PCTPublication No. WO 01/93953, entitled “NEUROMODULATION THERAPY SYSTEM,”and U.S. Pat. No. 7,228,179, entitled “METHOD AND APPARATUS FORPROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” which are incorporatedherein by reference.

As previously discussed, implantable pulse generators (and typicallymany active implantable medical devices) include a processor,microcontroller, or similar circuitry to control the operations of thedevice. The electronics of such devices are subject to faults. Many ofthe faults are mitigated by known fault handling mechanisms implementedwithin software of the device. However, there are number of faults thatare not subject to mitigation through conventional fault handlingmechanisms. For example, if a critical bit in flash memory becomesflipped, the implanted device may become inoperable or may operate in anunintended, unacceptable manner. The communication capabilities of thedevice may also be lost thereby making device diagnostics impossible. Insuch conventional circumstances, the implanted device is simplyexplanted from the patient and replaced with another device.

Some representative embodiments provide a mechanism for resetting animplantable medical device into a safe mode or a boot mode (using amodulated magnetic). From the safe mode or boot mode, it may be possibleto diagnose device faults and repair the faults (if necessary). Forexample, from the safe mode or boot mode, any memory corruption of thedevice may be corrected by rewriting the device code through wirelesscommunications supported by the safe mode or boot mode. As used herein,the term “reset” is intended to take its ordinary meaning as applied toa reset of a processor. As known in the art, a reset typically involvesplacing related logic elements or peripherals (that are controlled bythe processor) into a known state. Also, the reset typically involves“vectoring” to a known location to begin execution of binary code atthat location, where the binary code invokes certain initializationoperations.

FIG. 3 depicts controller 160 and a portion of pulse generator 150during reset operations according to one representative embodiment.Controller 160 may include suitable code for initiating a resetoperation when pulse generator 150 becomes non-functional. The resetoperation may be employed to attempt to diagnose any potential issuesand to reestablish operation of pulse generator 150 (if possible). Byattempting such operations, some amount of otherwise unnecessary explantsurgeries may be avoided.

In operation, controller 160 may drive current through coil 166 togenerate a modulated magnetic field. In some embodiments, controller 160initially drives a RF signal through coil 166. When coil 166 is placedadjacent to magnetic receiver component 153 of pulse generator 150(across the tissue barrier 350), the magnetic field causes component 153to generate a signal related to the modulated magnetic field. Thegenerated signal is than optionally processed by circuitry 301 (ifdeemed necessary).

In one embodiment, component 153 may be implemented using a giantmagnetoresistive (GMR) device or sensor. GMR sensors typically employthin film structures composed of ferromagnetic alloys sandwiched aroundan ultrathin nonmagnetic conducting middle layer. The thin filmstructures exhibit a large change in resistance (typically 10 to 20%)when the sensors are subjected to a magnetic field, compared with amaximum sensitivity of a few percent for other types of magneticsensors. That is, ferromagnetic layers transition between anti-paralleland parallel magnetic moments depending upon whether an externalmagnetic field is applied. In turn, the anti-parallel and parallelorientations of the ferromagnetic layers changes the resistance of theconductive layer via electron spin states in the ferromagnetic layersadjacent to the conductive layer, Digital GMR sensors are commerciallyavailable (such as from NVE Corporation, Eden Prairie, Minn.) which maybe employed for component 153.

Circuitry 301 may be optionally employed to process (e.g., filter,demodulate, etc.) the time-varying signal from component 153 andcommunicates a bit stream generated by the processing operations toreset logic 303. Reset logic 303 stores a window of the bit stream inmemory reset logic 303. Reset logic 303 monitors the bit stream toidentify one or more predefined sequence of bits. The predefinedsequence of bits may define a key to cause reset logic 303 to resetcontroller 151 or to cause controller 151 to execute code 311 thatdefines a safe mode of operations of pulse generator 150. Reset logic303 may be implemented using any suitable electronic logic circuitryaccording to, for example, conventional digital logic design techniques.If desired, a limited set of Instructions may be stored in electronicmemory for implementation of reset logic 303.

In some embodiments, reset logic 303 is connected to the reset pin ofcontroller 151 through reset line 304. In the event that reset logic 303detects the appropriate reset key in the bit stream generated from themodulated magnetic field, reset logic 303 asserts a suitable logicsignal on line 304. The signal on line 304 causes controller 151 toconduct a reset (which is known in the art). That is, controller 151begins to execute code programmed into its non-volatile memory 310 suchas a bootstrap loader program. The bootstrap loader program may initiatecertain system operations and, in turn, load the fully functionalapplication code 312 to control pulse generator 150. After communicatingthe defined key for a system reset, external controller 160 may thenattempt to conduct conventional communications (e.g., through near fieldor far field telemetry) with pulse generator 150 to determine whetherthe pulse generator 150 has returned to a properly functioning state, ifno response is obtained through telemetry attempts after communicatingthe reset key, it may be assumed that the reset attempt was unsuccessfulin resolving the system fault.

In one embodiment, the bootstrap loader program (executed after reset)may perform a verification of or an integrity check of software orfirmware code stored in memory 310 (e.g., using a checksum operation orCRC operations, etc.). if a memory error is detected, the bootstraploader program may automatically default to a safe mode of operation(e.g., as defined by code 311).

In some embodiments, reset logic 303 may communicate other logic signalsto controller 151 in an attempt to resolve a fault in pulse generator150. As shown in the specific embodiment of FIG. 3, reset logic 303includes polling line 305 and logic signal line 306. Rest logic 303 mayset a flag via polling line 305 after a reset operation of controller151 has occurred. When controller 151 detects the flag as set via logicsignal line 306, controller 151 may then execute code stored in memory310 of controller 151. The executed code may be adapted to permitrecovery and/or repair of pulse generator 150 (e.g., to permit are-write of system code in memory 310 or elsewhere in pulse generator150). For example, code 311 may be adapted to implement a “safe mode”mode of operation of pulse generator 150 in which a minimum number ofsystem operations are performed to permit software to be reloaded intopulse generator 150. The software/firmware update may be performed bycode 311 using conventional operations which are known in the art.

In some embodiments, reset logic 303 may communicate different logicstates on logic signal line 306. For example, reset logic 303 maycommunicate a vector to identify code for execution (e.g., safe modecode 311) after polling operations. Also, depending upon the datacommunicated in this manner, the executed code may perform differentfunctions. For example, different data values may be employed fordiagnostic, operations, external communications with controller 160,software reload operations, etc.

Although it is not a critical requirement of the invention, reset logic303 is preferably provided within pulse generator 150 to operateindependently of microcontroller 151. By providing independentoperation, if microcontroller 151 enters a non-recoverable state due toa hardware or software fault, it is possible to reestablish properoperation of the implant device without physically accessing the device.Further, in some embodiments, the reset operations are implemented insuch a manner that extraneous signals will not inadvertently cause adevice reset. A specific sequence of operations (e.g., communication ofone or more digital keys) may be required as a condition before thereset signal is provided to the microcontroller or processor.

FIG. 4 depicts a flowchart for attempting to recover proper functioningof a medical device implanted within a patient. In 401, the patientinitially reports that the patient's implant device is non-responsive.The patient may have previously noticed that the therapy provided by theimplant device is no longer being delivered. Additionally oralternatively, the patient may have previously noticed that the implantdevice is not responsive to communication attempts by the patient'sexternal controller device.

In 402, conventional wireless communications (near field or far field)are attempted using clinician device. In 403, it is determined whetherthe communication attempt was successful. If so, implant device faults(if any) are resolved using conventional communications (404).

In 405, if the conventional wireless communications are unsuccessful, amodulated magnetic field is provided. The reset functionality mayrequire the modulated magnetic field to be provided at or near a definedfrequency to permit the reset functionality to be activated (e.g., usingband-pass filtering of the resulting signal in the pulse generator).

In 406, a digital key is communicated for the reset logic of the pulsegenerator via the modulated magnetic field. Although a digital key ismentioned according to some embodiments, any suitable message sequence,format, or protocol may be employed according to other embodiments. Uponreceipt, the reset logic of the device (assuming some level ofoperability still exists in the implanted device) causes themicrocontroller or processor to be reset by asserting a suitable logicsignal on the reset pin of the microcontroller or processor. A safe modeof operation may be employed upon reset. The safe mode may be initiatedusing further operations of the reset logic (e.g., according to aparameter value communicated with or after the reset key).Alternatively, the safe mode of operation may be a default state afterreset

After attempting reset operations by communication of the digital key,in 407, an attempt to establish communications with the implantedmedical device is performed (e.g., using near field or far fieldcommunications). In 408, it is determined whether the communicationattempt was successful. If successful, software is reloaded into implantdevice (409) and further diagnostic operations may be optionallyperformed (410), if desired. The software/firmware update may beperformed using conventional protocols, which are known in the art, orany subsequently developed protocol. If the communications attempt isnot successful, it is concluded that an explant procedure to remove theimplanted device from the patient's body may be necessary (411).

Although certain representative embodiments and advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the appended claims. Moreover, the scope of thepresent application is not intended to be limited to the particularembodiments of the process, machine, manufacture, composition of matter,means, methods and steps described in the specification. As one ofordinary skill in the art will readily appreciate when reading thepresent application, other processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the described embodiments maybe utilized. Accordingly, the appended claims are intended to includewithin theft scope such processes, machines, manufacture, compositionsof matter, means, methods, or steps.

1. An implantable medical device, comprising: a therapy module adapted to provide a therapy to a patient after implantation in the body of the patient; a processor adapted for central control of the implantable medical device a magnetic sensor for sensing an external magnetic field: and reset logic that is independently operable from a processor of the implantable medical device and that is adapted to (i) detect a digital key in digital data generated from a modulated magnetic field detected by the magnetic sensor; (ii) in response to detecting the digital key in the digital data, asserting a reset signal on a pin of the processor by the reset logic; wherein the processor is adapted to conduct reset operations in response to assertion of the reset signal on the reset pin of the processor.
 2. The implantable medical device of claim 1 wherein the implantable medical device comprises memory storing a first set of software instructions of a safe mode of operations that are different from a second set of software instructions of an application mode of operations wherein the application mode of operations controls provision of a therapy by the implantable medical device to the patient.
 3. The implantable medical device of claim 2 wherein the reset logic is operable to cause the processor to execute the first set of software instructions after the processor is reset.
 4. The implantable medical device of claim 2 wherein the first set of software instructions comprises code for performing a software or firmware update.
 5. The implantable medical device of claim 2 wherein the first set of software instructions comprises code for performing an integrity check of software or firmware of the implantable medical device.
 6. The implantable medical device of claim 2 wherein the reset logic is connected to the processor by a polling line.
 7. The implantable medical device of claim 6 wherein the reset logic is operable to cause the processor to execute the first set of software instructions by communicating a signal on the polling line after reset operations.
 8. The implantable medical device of claim 2 wherein the magnetic field sensor is a giant magnetoresistive (GMR) sensor.
 9. The implantable medical device of claim 8 wherein the GMR sensor is a digital sensor. 